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Using onClickListener in Recycler View with Retrofit Structure - Kotlin

Hello i have a recyclerview that is filled with some data coming from a Webservice, using Retrofit.
Now I want to implement a onClickListener, so when i click each row of the Recycler View, i can see more data from that object, and tried to work with some examples, but i got stucked
Here is my adapter. I know that in the onCreateViewHolder, i should put in the Return AnunciosViewHolder a second parameter, of the type cellClickListener, but i have no idea what i have to put. I tried this#CellCLickListener and this#cellCLickListener and it gave me error that is is unresolved
class AnuncioAdapter(val anuncios: List<Anuncio>): RecyclerView.Adapter<AnunciosViewHolder>() {
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): AnunciosViewHolder {
val view = LayoutInflater.from(parent.context).inflate(R.layout.recyclerline, parent, false)
return AnunciosViewHolder(view)
}
override fun getItemCount(): Int {
return anuncios.size
}
override fun onBindViewHolder(holder: AnunciosViewHolder, position: Int) {
return holder.bind(anuncios[position])
}
}
class AnunciosViewHolder(itemView : View, private val cellClickListener: CellClickListener): RecyclerView.ViewHolder(itemView){
private val morada: TextView = itemView.findViewById(R.id.morada)
private val telemovel: TextView = itemView.findViewById(R.id.number)
private val fotografia: ImageView = itemView.findViewById(R.id.image)
fun bind(anuncio: Anuncio) {
morada.text = anuncio.morada
telemovel.text = anuncio.telemovel
itemView.setOnClickListener {
cellClickListener.onCellClickListener(anuncio)
}
I also tried creating an interface
interface CellClickListener {
fun onCellClickListener (data: Anuncio)
}
and in my Activity i put this method and it gives me an error that «overrides nothing»
override fun onCellClickListener(data: Anuncio) {
val intent = Intent(this#ListaAnuncios, DetalhesActivity::class.java)
intent.putExtra(PARAM_ID, data.id.toString())
intent.putExtra(PARAM_MORADA, data.morada)
intent.putExtra(PARAM_TELEMOVEL, data.telemovel)
startActivityForResult(intent, newAnuncioActivityRequestCode1)
Log.e("***ID", data.id.toString())
}
UPDATE
After using the suggestions made by Praveen i was able to clean my Adapter from errors, however i am struggling in the activity part
if it put
val anuncioAdapter = AnuncioAdapter(anuncios, this)
on the beggining of my On Create, it doesn't recognize «anuncios»
However i am declaring my adapter inside the call.enqueue
recyclerView.apply {
setHasFixedSize(true)
layoutManager =
LinearLayoutManager(this#ListaAnuncios)
adapter = AnuncioAdapter(response.body()!!)
}
And it is asking to pass an instance of cellClickListener here, but if i use «this» in here, it is stated that i am trying to pass an instance of the recycler view instead of the CellClickListener
NEW UPDATE
Forgot to put all the call.enqueue method
call.enqueue(object : Callback<List<Anuncio>> {
override fun onResponse(call: Call<List<Anuncio>>, response: Response<List<Anuncio>>) {
if (response.isSuccessful){
recyclerView.apply {
setHasFixedSize(true)
layoutManager =
LinearLayoutManager(this#ListaAnuncios)
adapter = AnuncioAdapter(response.body()!!)
}
}
}
override fun onFailure(call: Call<List<Anuncio>>, t: Throwable) {
Toast.makeText(this#ListaAnuncios, "${t.message}", Toast.LENGTH_LONG).show()
}
}) }
i tried both approaches of #Praveen and #aligur, but still struggling with asking me to put the instance of Clicklistener as the 2nd parameter, but using «this» is putting the instance of the Recycler View and not of the ClickListener
Thank You in advance

and in my Activity i put this method and it gives me an error that
«overrides nothing»
You are not implementing CellClickListener in your activity. Add CellClickListener after your activity's class name declaration
class MainActivity : AppCompatActivity(), CellClickListener {
}
I know that in the onCreateViewHolder, i should put in the Return
AnunciosViewHolder a second parameter, of the type cellClickListener,
but i have no idea what i have to put. I tried this#CellCLickListener
and this#cellCLickListener and it gave me error that is is unresolved
You've to add the private val cellClickListener: CellClickListener parameter to the constructor of AnuncioAdapter, not the ViewHolder. Only then you will be able to pass it from your activity.
Change constructor of AnuncioAdapter to accept a CellClickListener and remove the same from the constructor of AnunciosViewHolder
class AnuncioAdapter(
private val anuncios: List<Anuncio>,
private val cellClickListener: CellClickListener
): RecyclerView.Adapter<AnunciosViewHolder>() {
}
To access this cellClickListener inside AnunciosViewHolder you've to make it an inner class of AnuncioAdapter, which you can make, as it's already tightly coupled with the adapter.
inner class AnunciosViewHolder(itemView : View): RecyclerView.ViewHolder(itemView){
}
Now, on creating an object of AnuncioAdapter inside activity, just pass an instance of cellClickListener using this, as it's already implementing it.
val anuncioAdapter = AnuncioAdapter(anuncios, this)

I think the easiest way is passing function as parameter to RecyclerViewAdapter.
for instance:
RecyclerViewAdapter(val clickListener : () -> Unit)
onCreateViewHolder(){
clickListener.invoke()
}
in your view
adapter = ReceylerViewAdapter({
//do your stuff here
})

Was finally able to find a solution. By Using #Praveen suggestion, and by finding this example https://github.com/velmurugan-murugesan/Android-Example/tree/master/RetrofitWithRecyclerviewKotlin/app/src/main/java/app/com/retrofitwithrecyclerviewkotlin
On the activity i added a new val, before the OnCreate method
lateinit var anuncioAdapter: AnuncioAdapter
Added this on the onCreate (so i could use the first sugestion)
val recyclerView = findViewById<RecyclerView>(R.id.recycler_view)
anuncioAdapter = AnuncioAdapter(this,this)
recyclerView.layoutManager = LinearLayoutManager(this)
recyclerView.adapter = anuncioAdapter
And changed the recyclerview.apply {} on the call.enqeue just to
anuncioAdapter.Anuncios(response.body()!!);
And finally created the Anuncios Method on the Adapter
fun Anuncios(anuncio: List<Anuncio>){
this.anuncios = anuncio;
notifyDataSetChanged()
}
With this it works like how i wanted id. Thanks for the help

How to disable the auto scroll of a RecyclerView (ListAdapter) that happens when an item is updated?

BACKGROUND
I have a UI that shows a list of users' fullnames with a like/dislike button for each item. I am using a ListAdapter that under the hood uses DiffUtil and AsyncListDiffer APIs. The list of users is received as a LiveData from a Room database and it's ordered by "isLiked".
PROBLEM
Whenever the like button is tapped, Room as I am using a LiveData will re-submit the new data to the adapter. The problem is that as the list is ordered by "isLiked", the liked user will change its position and the RecyclerView will always sroll to the new position.
I don't want to see the new position of the updated item. So, how can I disable the auto scroll behavior?
WHAT I TRIED
MainActivity.kt
..
val userAdapter = UsersAdapter(this)
val ll = LinearLayoutManager(this, LinearLayoutManager.VERTICAL, false)
recyclerView.apply {
layoutManager = ll
adapter = userAdapter
itemAnimator = null
setHasFixedSize(true)
}
viewModel.users.observe(this, {
// This will force the recycler view to scroll back to the previous position
// But it's more of a workaround than a clean solution.
val pos = ll.findFirstVisibleItemPosition()
userAdapter.submitList(it) {
recyclerView.scrollToPosition(pos)
}
})
..
UsersAdapter.kt
class UsersAdapter(
private val clickListener: UserClickListener
) : ListAdapter<UserEntity, UsersAdapter.UserViewHolder>(DIFF_CALLBACK) {
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): UserViewHolder {
val view = LayoutInflater.from(parent.context).inflate(R.layout.item_user, parent, false)
return UserViewHolder(view)
}
override fun onBindViewHolder(holder: UserViewHolder, position: Int) {
val userEntity = getItem(position)
holder.bind(userEntity, clickListener)
}
class UserViewHolder(view: View) : RecyclerView.ViewHolder(view) {
private val textView: TextView = view.findViewById(R.id.fullName)
private val fav: ImageButton = view.findViewById(R.id.fav)
fun bind(user: UserEntity, clickListener: UserClickListener) {
textView.text = user.fullName
val favResId = if (user.favorite) R.drawable.like else R.drawable.dislike
fav.setImageResource(favResId)
fav.setOnClickListener {
val newFav = !user.favorite
val newFavResId = if (newFav) R.drawable.like else R.drawable.dislike
fav.setImageResource(newFavResId)
clickListener.onUserClicked(user, newFav)
}
}
}
interface UserClickListener {
fun onUserClicked(user: UserEntity, isFavorite: Boolean)
}
companion object {
private val DIFF_CALLBACK = object : DiffUtil.ItemCallback<UserEntity>() {
override fun areItemsTheSame(
oldUser: UserEntity,
newUser: UserEntity
) = oldUser.id == newUser.id
override fun areContentsTheSame(
oldUser: UserEntity,
newUser: UserEntity
) = oldUser.fullName == newUser.fullName && oldUser.favorite == newUser.favorite
}
}
}
I tried using a regular RecyclerView adapter and DiffUtil with detect moves set to false.
I added the AsyncListDiffer as well.
I tried the ListAdapter, and even tried the paging library and used the PagedListAdapter.
DiffUtil's callback changes the auto scrolling, but i couldn't get the desired behavior.
Any help is greatly appreciated!

How to preserve scroll position of a RecyclerView after a configuration change when using MVVM viewmodel and livedata?

READ FIRST:
Apologies, it seems I have played myself. I was using RecyclerView in my xml earlier, but switched it over for CardStackView (it still uses the exact same RecyclerView adapter). If I switch back to RecyclerView, the original code below works - the scroll position is saved and restored automatically on configuration change.
I'm using a MVVM viewmodel class which successfully retains list data for a RecyclerView after a configuration change. However, the previous RecyclerView position is not restored. Is this expected behaviour? What would be a good way to solve this?
I saw a blog post on medium briefly mentioning you can preserve scroll position by setting the adapter data before setting said adapter on the RecyclerView.
From what I understand, after a configuration change the livedata that was being observed earlier gets a callback. That callback is where I set my adapter data. But it seems this callback happens after the onCreate() function finishes by which point my RecyclerView adapter is already set.
class MainActivity : AppCompatActivity() {
private val adapter = MovieAdapter()
private lateinit var viewModel: MainViewModel
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
val binding = ActivityMainBinding.inflate(layoutInflater)
setContentView(binding.root)
// Create or retrieve viewmodel and observe data needed for recyclerview
viewModel = ViewModelProvider(this).get(MainViewModel::class.java)
viewModel.movies.observe(this, {
adapter.items = it
})
binding.recyclerview.adapter = adapter
// If viewmodel has no data for recyclerview, retrieve it
if (viewModel.movies.value == null) viewModel.retrieveMovies()
}
}
class MovieAdapter :
RecyclerView.Adapter<MovieAdapter.MovieViewHolder>() {
var items: List<Movie> by Delegates.observable(emptyList()) { _, _, _ ->
notifyDataSetChanged()
}
class MovieViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {
private val binding = ItemMovieCardBinding.bind(itemView)
fun bind(item: Movie) {
with(binding) {
imagePoster.load(item.posterUrl)
textRating.text = item.rating.toString()
textDate.text = item.date
textOverview.text = item.overview
}
}
}
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): MovieViewHolder {
val view = LayoutInflater.from(parent.context)
.inflate(R.layout.item_movie_card, parent, false)
return MovieViewHolder(view)
}
override fun onBindViewHolder(holder: MovieViewHolder, position: Int) {
holder.bind(items[position])
}
override fun getItemCount() = items.size
}
class MainViewModel : ViewModel() {
private val _movies = MutableLiveData<List<Movie>>()
val movies: LiveData<List<Movie>> get() = _movies
fun retrieveMovies() {
viewModelScope.launch {
val client = ApiClient.create()
val result: Movies = withContext(Dispatchers.IO) { client.getPopularMovies() }
_movies.value = result.movies
}
}
}

Set adapter only after its items are available.
viewModel.movies.observe(this, {
adapter.items = it
binding.recyclerview.adapter = adapter
})

Saving the instance of Recycler view during orientation change

I have a RecyclerView which was build using an Arraylist. That Arraylist consists of User defined objects named ListItem.
Each recyclerview has a card view. Each CardView holds each ListItem.
I have removed one CardView from that RecyclerView.
When I rotate the screen , A new Activity is created which results in showing the old data. But I want the recyclerview to hold only updated list and should retain the scrolled position.
ListItem class :
class ListItem(var title: String, var info: String, val imageResource: Int) {
}
MainActivity class :
class MainActivity : AppCompatActivity() {
private lateinit var mSportsData: ArrayList<ListItem>
private lateinit var mAdapter: MyAdapter
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
val gridColumnCount = resources.getInteger(R.integer.grid_column_count)
recycler_view.layoutManager = GridLayoutManager(this,gridColumnCount)
mSportsData = ArrayList()
recycler_view.setHasFixedSize(true)
initializeData()
recycler_view.adapter = mAdapter
var swipeDirs = 0
if (gridColumnCount <= 1) {
swipeDirs = ItemTouchHelper.LEFT or ItemTouchHelper.RIGHT
}
val helper = ItemTouchHelper(object : ItemTouchHelper.SimpleCallback(ItemTouchHelper.LEFT or ItemTouchHelper.RIGHT or ItemTouchHelper.UP or ItemTouchHelper.DOWN,swipeDirs) {
override fun onMove(recyclerView: RecyclerView, viewHolder: RecyclerView.ViewHolder, target: RecyclerView.ViewHolder): Boolean {
val from = viewHolder.adapterPosition
val to = target.adapterPosition
Collections.swap(mSportsData,from,to)
mAdapter.notifyItemMoved(from,to)
return true
}
override fun onSwiped(viewHolder: RecyclerView.ViewHolder, direction: Int) {
mSportsData.removeAt(viewHolder.adapterPosition)
mAdapter.notifyItemRemoved(viewHolder.adapterPosition)
}
})
helper.attachToRecyclerView(recycler_view)
}
private fun initializeData() {
val sportsList : Array<String> = resources.getStringArray(R.array.sports_titles)
Log.d("Printing","$sportsList")
val sportsInfo : Array<String> = resources.getStringArray(R.array.sports_info)
val sportsImageResources : TypedArray = resources.obtainTypedArray(R.array.sports_images)
mSportsData.clear()
for (i in sportsList.indices-1) {
Log.d("Printing","${sportsList[i]},${sportsInfo[i]},${sportsImageResources.getResourceId(i,0)}")
mSportsData.add(ListItem(sportsList[i], sportsInfo[i], sportsImageResources.getResourceId(i, 0)))
}
sportsImageResources.recycle()
mAdapter = MyAdapter(mSportsData,this)
mAdapter.notifyDataSetChanged()
}
fun resetSports(view: View) {
initializeData()
}
}
MyAdapter class :
class MyAdapter(var mSportsData: ArrayList<ListItem>, var context: Context) : RecyclerView.Adapter<MyAdapter.ViewHolder>() {
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
return ViewHolder(LayoutInflater.from(context).inflate(R.layout.wordlist_item,parent,false))
}
override fun getItemCount() = mSportsData.size
override fun onBindViewHolder(holder: ViewHolder, position: Int) {
val listItem = mSportsData.get(position)
holder.bindTo(listItem)
}
inner class ViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView), View.OnClickListener {
init {
itemView.setOnClickListener(this)
}
override fun onClick(view: View) {
val currentSport = mSportsData.get(adapterPosition)
val detailIntent = Intent(context, DetailActivity::class.java)
detailIntent.putExtra("title", currentSport.title)
detailIntent.putExtra("image_resource", currentSport.imageResource)
context.startActivity(detailIntent)
}
fun bindTo(currentSport : ListItem){
itemView.heading_textview.setText(currentSport.title)
itemView.description_textview.setText(currentSport.info)
Glide.with(context).load(currentSport.imageResource).into(itemView.image_view)
}
}
}

You can restrict activity restarting in your Manifest if you have same layout for Portrait and Landscape mode.
Add this to your activity in the manifest.
<activity android:name=".activity.YourActivity"
android:label="#string/app_name"
android:configChanges="orientation|screenSize"/>
If you don't want to restrict screen orientation changes, then you can use OnSaveInstanceState method to save your older data when orientation changed. Whatever data you save via this method you will receive it in your OnCreate Method in bundle. Here is the helping link. So here as you have ArrayList of your own class type you also need to use Serializable or Parcelable to put your ArrayList in your Bundle.
Except these making ArrayList as public static is always a solution, But its not a good solution in Object Oriented paratime. It can also give you NullPointerException or loss of data, in case of low memory conditions.

It looks like initializeData is called twice since onCreate is called again on orientation change, you could use some boolean to check if data has been already initialized then skip initializing

What you are doing is you are deleting the values that are passed down to the recyclerview but when the orientation changes the recyclerview reloads from activity and the original data from activity is passed down again and nothing changes, so if you want to save the changes in recyclerview you have to change the original data in the activity so that if the view reloads the data is the same.

I think u initialize adapter in oncreate method in which the whole adapter will be recreated and all datas is also newly created when configuration changes. Because u init data in oncreate method. Try something globally maintain the list and also delete the item in the list in activity when u delete in adapter also. Or try something like view model architecture

Use MVVM pattern in the project. It will manage the orientation state.
MVVM RecyclerView example:
https://medium.com/#Varnit/android-data-binding-with-recycler-views-and-mvvm-a-clean-coding-approach-c5eaf3cf3d72

How to observe member variables of a class in MutableLiveData?

I am trying to observe fields of my class without exposing it. So far, I've tried this:
TaskItemViewModel.kt
open class TaskItemViewModel(private val navigator: ITaskNavigator) : ViewModel() {
private val taskItem: MutableLiveData<TaskItem> = MutableLiveData()
val title: LiveData<String?> = Transformations.map(taskItem) { it.title }
val content: LiveData<String?> = Transformations.map(taskItem) { it.content }
var showCheck: LiveData<Boolean> = Transformations.map(taskItem) { it.isCompleted }
fun setModel(model: TaskItem) {
this.taskItem.value = model
}
}
ItemListScreenAdapter.kt
class ItemListScreenAdapter(private val navigator: ITaskNavigator) : RecyclerView.Adapter<ItemListScreenAdapter.TaskItemViewHolder>() {
private val TAG = "ItemListScreenAdapter"
private var dataset: List<TaskItem> = listOf()
override fun onBindViewHolder(viewHolder: TaskItemViewHolder, position: Int) {
with(viewHolder.binding) {
this.viewModel?.setModel(dataset[position])
executePendingBindings()
}
}
fun updateDataset(dataset: List<TaskItem>) {
Log.d(TAG,"Updating dataset")
this.dataset = dataset
notifyDataSetChanged()
}
override fun getItemCount(): Int = dataset.size
override fun onCreateViewHolder(parent: ViewGroup, type: Int): TaskItemViewHolder {
val inflater = LayoutInflater.from(parent.context)
val binding = ItemTaskBinding.inflate(inflater, parent, false)
binding.viewModel = TaskItemViewModel(navigator)
return TaskItemViewHolder(binding)
}
class TaskItemViewHolder(val binding: ItemTaskBinding) : RecyclerView.ViewHolder(binding.root)
}
If I call setModel before inflating the view, everything works fine. However, after the view is inflated, the view is not updated even if taskItem 's value is updated. You can be assured that updateDataset is called everytime there is a change in dataset.
I want the view to be updated whenever I call setModel in corresponding viewmodel. What are the ways to achieve this?
For this viewmodel, I want to use ViewModel rather than BaseObservable. Therefore, please give your answers according to this.
EDIT:
I have found the solution to the problem.
in ItemListScreenAdapter's onCreateViewHolder method, after inflating, I needed to set LifeCycleOwner of the binding.
I added the following line after inflating the ItemTaskBinding.
binding.setLifecycleOwner(parent.context as MainActivity)
and the problem is solved and view is being updated.